With the fast social and economic development and the improving standard of living of people, the pollution of toxic substance, especially the organic matters which are hard to degrade, to the natural environment gets aggravated. The wastewater of such industries as dyeing and printing, pharmacy, and chemical, garbage leachate and urban sewage sludge may all contain a great number of organic matters which are hardly degradable. As such pollutants are not easy to degrade, they may exist for a long period in environment, impacting regional or global environment with the conveying by air and water. They may finally impair the health of human beings seriously by way of food chain enrichment. The pollution of water is one of the serious environmental problems at present.
To remove organic pollutants from water is one of the hottest research subjects in the field of water treatment. With unremitting efforts of specialists in environmental science for dozens of years, a large group of effective treatment processes have been developed. Nonetheless, the existing treatment technologies, such as advanced oxidation and microbial degradation, fail to meet the requirements of pollution control due to the restrictions of such shortcomings as low treatment efficiency, high cost, production of secondary pollution, and incomplete degradation. In particular, for the treatment of wastewater of high concentration, the above methods can hardly be applied in a large scale due to disadvantages of large site area, stringent operation conditions, low adaptability, and low removal efficiency. As active carbon adsorption boasts significant advantages in treating the organic matters which are difficult to get degraded by bio-chemical process or soluble organic matters which can hardly be oxidated in the ordinary oxidation process, it is often employed in the treatment of organic wastewater of high concentration which is hard to degrade. In particular, with the increasing requirements for the treatment degree of wastewater and wastewater recycling rate in recent years, great importance has been attached to this efficient treatment process generally. For instance, the treatment of wastewater containing oil, phenol, nitro compound, chlorine-radical or nitro substituted aromatic compound, heterocyclic compound, synthetic dyes and DDT, etc. However, the holes of active carbon (including tiny, middle and large holes) are in extensive distribution, so its adsorption lacks selectivity. Additionally, active carbon is of high hydrophilicity, so the efficiency to adsorb organic pollutants in water is low. The active carbon after adsorption will generally be regenerated by heating for recycling. In the conventional thermal regeneration, active carbon would get lost significantly in the process of regeneration, and the adsorbing capability of the regenerated active carbon would decline obviously. In addition, the tail gas produced upon the regeneration would cause such problems as secondary pollution to the atmosphere. Compared with the conventional thermal treatment, microwave treatment boasts significant advantages in the regeneration of active carbon. As active carbon has a high capability in absorbing microwave, its temperature will rise quickly under microwave, and the heated pollutants adsorbed on the surface will get degraded and desorbed. Nonetheless, the microwave energy will cause great damage to active carbon, so it is only suitable for short-term treatment. To be exposed to the microwave radiation for a long period will lead the surface of active carbon to catch fire and the hole structure after regeneration will also be destructed. As a result, the specific surface area will decrease significantly. Besides, because the active carbon has a strong capability in absorbing microwave, the microwave energy cannot penetrate active carbon deeply and the adsorption column cannot be heated evenly. As a result, it can be often found that some active carbon in some space cannot be regenerated or be regenerated completely as no microwave radiation reaches, whereas some other has its temperature risen too high and gets the structure damaged seriously. As active carbon absorbs microwave energy, the penetrability of microwave in the active carbon layer is very poor. This greatly limits the size of adsorption column. Therefore, it remains a hard nut for us to treat the organic pollutants, especially persistent organic matters, in water. We should keep on exploring and researching in the area. It is of great significance to protecting water environment and reducing risks to the health of human to design and develop new technologies to degrade organic pollutants with a view to removing organic pollutant effectively while not causing secondary pollution and applying such technologies in the treatment of organic pollutants in water successfully.